In the related art, for a pixel driver circuit which controls a working current through a current source, a turning-on degree of a driving transistor is usually controlled by a capacitor structure at a display stage. After a grayscale value of a subpixel has been determined, a target current Itarget flowing through the driving transistor is determined too. However, at a charging stage, a current generated by the current source is equal to Itarget. In this way, it is impossible for the driver circuit to be applied to a display panel having a high resolution. In addition, in the case that this driver circuit is applied to a display panel having a low resolution, an effective display time period is reduced as well as a display effect may be deteriorated.